This invention relates to poly aluminum chloride products useful for all types of water treatment, and to methods for making. More particularly, this invention relates to poly aluminum chloride products having a mid-range basicity that are used in water treatment applications.
Poly aluminum chloride is used for water treatment to reduce turbidity, to remove color, to reduce TOC, to reduce filtering rates and the like. This material is a coagulant that produces a floc in water that settles out of solution. This floc traps various impurities and particles found in water, as well as removing color-forming bodies. The present commercial products are used to treat potable water, waste water, for paper treatment and sizing, for food industries and the like.
It would be highly desirable to develop a low cost process manufacturing process that can be carried out in existing aluminum sulfate facilities, and that produces an improved product in terms of basicity, cost and efficiency at lowering turbidity at low doses of product.
Various methods for making mid-basicity poly aluminum chlorides have been developed. Aluminum trihydrate can be reacted with hydrochloric acid or aluminum chloride; aluminum chloride can be reacted with an acid or a base, including calcium hydroxide or hydrated lime, sodium carbonate, acetic acid, citric acid, sodium hydroxide and sodium aluminate. When a small amount of phosphoric acid is added to aluminum chloride with a base such as hydrated lime as the co-reactant, the solubility of the lime is improved and, unexpectedly, performance of the product in terms of reducing settled and filtered turbidities at minimum dosage levels, is also improved.
The methods used to prepare the poly aluminum chloride products of the invention can be described broadly in terms of whether an external heat source is required to initiate or maintain a reaction or not. Both methods are successful.
However, when an external heat source is not required, the costs of making the water treatment product of the invention are reduced considerably.